1. Field of the Invention
The present invention relates to a suspension system in connection with a saddle on a two-wheeled vehicle, preferably a bicycle. More precisely the invention concerns a seat suspension assembly to be mounted, e.g. on a standard bicycle, at the place on a bicycle frame where a normal seat post is inserted into a seat tube. A standard type saddle shall then be mounted on top of the seat suspension assembly.
2. Description of the Related Art
There are several types of previously known suspensions in connection with bicycle and motorcycle saddles.
Among the more recent types of suspensions for bicycle seats, is one in which the seat has a spring action in a direction along the seat tube in a telescopic assembly, which in most bicycles is slanted down toward the crank bearing. This type of suspension has a clear limitation in that the travel of the assembly along the seat tube during a spring action is in a direction that can deviate from the desired direction by as much as 45.degree.. This is so because, the upward movement a saddle makes during a blow that pushes the rear wheel upward is obliquely forward/upward, and not obliquely downward/forward in the direction of the seat tube. The above mentioned suspension also exhibits limitations with respect to travel. This is so because, the movement in the wrong direction will become more noticeable the longer the travel is, and will be quite perceptible when the bumps encountered are larger than a certain size, typically 10-15 mm.
A springy seat device for a two-wheeler, in particular a bicycle or a mountain bike, is previously known from Norwegian patent no. 300.168. The seat suspension assembly disclosed in NO 300.168 is based on a parallelogram solution that provides the correct type of travel during suspension movement, but the built-in spring thereof is mounted between two diagonally situated bearings in the parallelogram construction. Because of this, the seat suspension assembly has the limitation that in order to adapt the seat suspension assembly to the weight of the bicyclist, the spring must be replaced by another spring that is more or less compliant. In order to do this, the complete assembly must be disassembled, a new spring must be inserted, and thereafter the assembly must be reassembled.
It is important to provide an easy option for adapting the suspension to variable conditions, such as actual weight on the saddle. During slow bicycling, where the bicyclist will often sit in a rather erect position, more weight will be transferred to the saddle, than in the case when the bicycling is rapid and the bicyclist leans more forward over the handlebars. In this latter case, a larger portion of the weight is shifted forward and away from the saddle, and in these two situations, more or less compliant springs in the assembly will be of use. A bicyclist may be interested in a more or less compliant suspension in relation to the track he/she is about to bicycle through. If the track is complicated, with low speed to match, a different seat compliance will be desirable than if the track on average allows for higher speeds.
Such matters can be compensated for somewhat through an adjusted spring bias, but such a bias does not make the spring stiffer, i.e. the spring characteristic is not changed.
The suspension will easily become too stiff when using a strong spring, irrespective of how low a bias is chosen, and hence will work poorly on small bumps. Experience has also shown that it is difficult to find the correct spring compliance immediately, because the spring characteristic is as dependent on weight as on riding style. Changing the spring characteristic may become necessary during a development period of a bicyclist, e.g. during a weight reduction period. Consequently, it is impossible to state what is correct for the individual at any particular time. It is therefore desirable to be able to experiment on the spring rate of the seat suspension assembly.